In recent years, there has been advancement in the development of light emitting devices with light emitting units having organic electroluminescence (EL) elements. An organic EL element is configured of an organic layer interposed between first and second electrodes. The organic layer is generally configured of a light emitting layer interposed between a hole injection layer and an electron injection layer.
On the other hand, as a method of increasing luminance of a light emitting device, there is a method of stacking the foregoing organic layers and disposing a charge generation layer between mutually adjacent organic layers, which is a so-called multiphoton light emission structure or a tandem structure. For example, Patent Document 1 discloses using a configuration of stacking an n-doped organic layer, a metal compound layer, and a p-doped organic layer in this order as a charge generation layer. Patent Document 1 discloses that the metal compound layer may be selected from titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, manganese, iron, ruthenium, rhodium, iridium, nickel, palladium, platinum, copper, zinc, silicon, germanium, or a stoichiometric oxide or a nonstoichiometric oxide of a combination thereof.
Patent Document 2 discloses stacking LiF, Al, and 1, 4,5,8,9,12-hexaazatriphenylene hexa-carbonitrile (HATCN) as a charge generation layer.